Continental extension of northern Gondwana margin in the Eastern Himalaya: Constraints from geochemistry and U–Pb zircon ages of mafic intrusives in the Siang window, Arunachal Himalaya, India

Abstract

We report new U-Pb zircon age and whole-rock geochemical data from the Pangin mafic intrusive rocks of the Siang window, eastern Himalayas. These mafic rocks are medium to coarse-grained gabbros, consisting mainly of plagioclase and clinopyroxene with accessory phases (hornblende + Fe-Ti oxides) that retain granular and interlocking texture. Geochemically, they display enriched-mid oceanic ridge basalt (E-MORB) affinity characterized by moderate to slightly fractionated REE patterns marked by (La/Yb) N = 2.65 − 3.99. Their geochemical characteristics suggest that the parental magmas of these rocks were formed by medium to higher degrees (∼12-28%) of partial melting similar to that of the asthenospheric mantle in the garnet-spinel transition zone. Magmatic zircons from two gabbros yield U-Pb ages of 521.50 ± 2.53 Ma and 568 ± 2 Ma. This new age reveals two pulses of Late Neoproterozoic and Early Cambrian mafic magmatism that are inconsistent with the temporal distribution of Paleozoic magmatism in the Siang window of the Eastern Himalayas. However, based on the results of this study and the correlation of continental extensional mafic magmatism in the Northwest Himalaya, we suggest that investigated mafic intrusive rocks might have been generated in an extensional tectonic environment during the long-lasting Pan-African orogenic cycle of the late Neoproterozoic to early Cambrian which ended with the formation of the Gondwana supercontinent.

Genesis of meta-gabbroic crustal xenoliths found in Neogene/Quaternary alkali olivine basalt, northeastern Iran

“…These rocks are gneisses and schists, recrystallized limestones and dolomites, and granite and quartz diorite plutons similar to exposures of Neoproterozoic to Early Palaeozoic basement in other tectonic zones of Iran (Hassanzadeh et al 2008). The granites and quartz diorites and rhyolites in NE Iran range in age from 570 to 530 Ma (Bagherzadeh et al 2015;Shafaii Moghadam et al 2017a, b;Oinam et al 2020;Kumar & Pundir, 2021;Samadi et al 2022;Azizi & Whattam 2022). Late Neoproterozoic -Early Palaeozoic mafic and felsic intrusive igneous rocks and associated clastic sediments are also reported from other areas in Iran (Horton et al 2008;Bagherzadeh et al 2015;Shafaii Moghadam et al 2017a, b;Mazhari et al 2019;Sepidbar et al 2020;Azizi & Whattam, 2022), as well as other areas along the northern margin of the Gondwana supercontinent (Hassanzadeh et al 2008;Oinam et al 2020;Kumar & Pundir, 2021;Samadi et al 2022).…”

The Kerguelen mantle plume activity in Sylhet Trap mafic rocks of Southern Shillong Plateau, NE India: Implications for its role in magmatism of eastern India

“…Plate reconstruction shows that the first leading phase was recorded in the Eastern Tethyan Himalaya (ETH Tibet) in the Lower Cretaceous ultramafic-mafic, and felsic igneous activities are recorded in the entire Himalayan zone, particularly in the ETH (130-147 Ma) (Shi et al, 2018) in the Comei igneous province and the break-up between Greater India and Bunbury in western Australia initiated at 136-137 Ma which continued for a few million years (Gibbons et al, 2013). In the Eastern Lesser Himalaya (ELH), India, Lower Cretaceous Abor magmatic events have been recorded at 130-135 Ma (Oinam et al, 2020;Singh et al, 2021). Eastern India Ocean (EIO), the western region of Australia in the EIO, several islands including Naturaliste Plateau, Wallaby Plateau, Gulden Draak and Dirck Hartog Ridge also witnessed Lower Cretaceous magmatism (127-132 Ma) (Direen et al, 2017;Olierook et al, 2016Olierook et al, , 2017.…”

Petrogenesis of mantle peridotites in Neo‐Tethyan ophiolites from the Eastern Himalaya and Indo‐Myanmar Orogenic Belt in the geo‐tectonic framework of Southeast Asia

“…At the core of the Siang window of the Eastern Himalayan Syntaxis, metasedimentary rocks of the Miri-Buxa Group are interbedded and co-folded with volcanic rocks and sedimentary rocks of the Yinkiong Formation (Acharyya, 2007;Oinam et al, 2022;Singh, 1993, Singh, 2006Singh et al, 2019;Singh & Singh, 2012). The volcanic rocks are underlain by the Miri quartzite, whereas the mafic intrusives are mostly intruded into the Miri quartzite (Oinam et al, 2020;Singh, 2007Singh, , 2012Singh et al, 2021b). The rock units within the window are dissected by several subsidiary normal faults oblique to both the Main Boundary Thrust (MBT) and the North Pasighat Thrust (NPT) (Acharyya, 2007;Kumar, 1997).…”